[Feature] Create forum channels with default layout (#2646)

src/Discord.Net.Rest/API/Rest/CreateGuildChannelParams.cs

@@ -46,6 +46,9 @@ namespace Discord.API.Rest
         [JsonProperty("default_sort_order")]
         public Optional<ForumSortOrder?> DefaultSortOrder { get; set; }
 
+        [JsonProperty("default_forum_layout ")]
+        public Optional<ForumLayout> DefaultLayout { get; set; }
+
         public CreateGuildChannelParams(string name, ChannelType type)
         {
             Name = name;

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -400,7 +400,8 @@ namespace Discord.Rest
                 IsNsfw = props.IsNsfw,
                 Topic = props.Topic,
                 DefaultAutoArchiveDuration = props.AutoArchiveDuration,
-                DefaultSortOrder = props.DefaultSortOrder.GetValueOrDefault(ForumSortOrder.LatestActivity)
+                DefaultSortOrder = props.DefaultSortOrder.GetValueOrDefault(ForumSortOrder.LatestActivity),
+                DefaultLayout = props.DefaultLayout,
             };
 
             var model = await client.ApiClient.CreateGuildChannelAsync(guild.Id, args, options).ConfigureAwait(false);